I had this same issue with previous version screwing up Revit 2012 and it seemed there was a hotfix for this. Is there a hotfix this year? The updates haven't helped.

Basically the problem is that while I'm working in 2013, vital portions of the ribbon will not show up. Example, selecting a filled region, the button to edit boundary doesn't show up) You can get around this by cycling through the ribbon settings (collapse/un-collapse) but this is obviously very time-consuming to do for every command.

I know that it has something to do with Revit installing the .NET framework when i installed 2015, i just have no idea how to fix my issue with the previous installations.

Thanks.